RV Solar Panel advise?

Anyone know anything about RV solar panels? I'm looking at buying one for maintaining my battery while dry camping. The descriptions for the different sizes all seem to be the same (vague). Why would I want to spend more to get the 18 watt version when the 5 or 10 watt does the same job? Do the higher watt units charge a battery faster? I am looking at this Battery Tender unit.

http://www.campingworld.com/shopping/item/10-watt-charger-solar-panel/60087

Any recommendations would be appreciated!

 

I will start off by saying i have no practical experience with any of the products you are looking at, but i will give you my 2 cents.

Basically the higher wattage panels will theoretically be able to put out a little more juice and charge slightly faster.

The link you posted says that panel is rated at 540 milliamps. this random 18 watt panel that i googled here. is rated at 1.2 amps. so basically the 18 watt is putting out twice as much at peak power.

One thing i didn't quite understand about you post was if this was strictly for storage? because that's all either of these will be good for. if you want something to maintain a charge while you are using the battery, then you need something that puts out a lot more.

 

I'd call will at Sierra expeditions. He's a guru with these things